The invention pertains to multiple station, multiple clamp assembly blow molding machines for the manufacture of bottles and the like. In particular, the invention pertains to various improvements in mechanisms for clamping the molds together, stretching the extruded parison and pre-finishing the bottle at the opening thereof.
Multiple station blow molding machines are usually of circular or rotary configuration wherein the machine comprises a plurality of stations located about a circular path. Usually the machine includes a plurality of clamp assemblies, each containing a mold for one or more bottles. The total number of clamp assemblies usually equals the total number of stations. The clamp assemblies rotate from station to station about the circular path with various operations taking place either at the various stations which are of fixed location, or during movement between stations.
In a typical machine each clamp assembly requires a mechanism for closing and opening the clamp assembly to thereby close and open the mold therein and means to assure that the mold remains tightly clamped together during the blowing and prefinishing stages of making the bottle. Modern machines typically use a cam or hydraulic pressure mechanism for opening and closing the clamp assembly with cam action or hydraulic pressure providing for tight closure at the end of the closing stroke. A hydraulic or other actuator is attached to each clamp assembly and moves with the clamp assembly about the circular path of the machine. Such a machine therefore requires a separate actuator for each clamp assembly and means to supply hydraulic power to the actuator as it moves about the circular path.
The toggle action clamp assembly locks the molds tightly together at the end of the toggle linkage stroke. The hydraulic actuator is continuously pressurized to assure that the molds remain tightly joined until blowing and pre-finishing are completed and the bottle is ready to be ejected from the mold.
Pre-finish devices for blow molding machines-typically are combined with the blow pin assembly, either of which or both, may be moveable vertically. The vertical movement is actuated by a cam or a crank mechanism at the appropriate moment during the blow molding cycle. The cam mechanism is extensive in length and complicated to manufacture because the entire clamp assembly supporting the blow pin and pre-finish unit moves relative to the cam, the cam being fixed to the base of the machine.
Stretching means for stretching the lower end of a parison into an oblong shape also require a complicated mechanism. The stretching means are actuated with a mechanism separate from the support that carries the stretching means on a moveable clamp assembly. The stretching means usually comprises a single upwardly extending pin spaced from a blow pin pre-finish unit. The single pin and blow pin of the stretching means are actuated to move in opposite directions at appropriate moments in the machine cycle and therefore are typically cam operated. Thus, a complicated actuation mechanism is required for stretching means that are mounted on a machine which moves the bottle blowing apparatus, clamp assembly and molds from station to station about the machine. Applicant's invention disclosed below is directed to improved and more effective mechanisms incorporated in a multi station, multi clamp assembly blow molding machine.